In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drive train, but must do so while maintaining reasonable levels of performance, range, reliability, safety and cost.
In recent years there have been several incidents of a rechargeable battery pack, either contained within a laptop computer or utilized in a vehicle, catching on fire. As a result, one of the primary issues impacting consumer confidence with respect to both hybrid and all-electric vehicles is the risk of a battery pack fire.
Rechargeable batteries tend to be relatively unstable and prone to thermal runaway, an event that occurs when a battery's internal reaction rate increases to such an extent that it is generating more heat than can be withdrawn. If the reaction rate and generation of heat go unabated, eventually the heat generated becomes great enough to cause the battery and materials in proximity to the battery to combust. While thermal runaway is typically the result of a battery short or a manufacturing defect, damage such as that which may occur during an accident or when road debris dents or punctures the battery pack may also lead to a thermal runaway event.
Due to the risk of a battery pack fire, hybrid and electric vehicle (EV) manufacturers use a variety of techniques to shield their battery packs from the possible damage that may result from road debris or a vehicle collision. For example, in a vehicle using a relatively small battery pack such as a hybrid, the pack may be protected by placing it within the rear trunk, behind the rear seats, under the front seats, or in another comparatively well protected location. Vehicles utilizing large battery packs typically are forced to mount the pack under the car. To protect such a pack, a ballistic shield may be located between the road surface and the bottom of the pack as disclosed in U.S. Pat. Nos. 8,286,743 and 8,393,427.
Although the prior art teaches a variety of mounting techniques that can either be used to place the battery pack in a relatively protected region of a car or to otherwise shield the battery pack from potential harm, given the severity of the consequences accompanying a thermal runaway event, techniques for minimizing the effects of such an event are desired. The present invention provides a detection system that may be used to monitor for possible battery pack damage, thereby helping to decrease the likelihood of a damaged battery pack leading to a catastrophic battery pack event.